Field of the Invention
The present invention relates to a method for transferring a signal from a first electronic unit, which contains a signal source, to a second electronic unit, which contains a signal sink, in a system which comprises at least two electronic units.
The signal to be transferred is an analog signal or a digital signal.
A variety of techniques and devices are known in the art for transmitting signals from a first electronic unit to a second electronic unit in a system. In systems wherein no electrical isolation is required between the two electronic units between which a signal exchange will take place, there is typically a line connection between the first electronic unit and the second electronic unit. In complex systems such as a motherboard of a computer, wherein a signal exchange must take place between complex integrated modules, there is usually a data bus present which connects the individual modules such as the memories, processors, and controllers to one another. The signal transfer requires that additional modules be interposed between the signal sources or sinks and the bus. From the signals that are to be transferred, these modules generate signals with levels that are high enough for transfer over the bus.
In order to connect the mutually communicating individual modules of a complex system to one another by means of a bus system, these modules are usually installed on multi-layer motherboards, with electrically conductive connections inserted between individual layers in order to realize the bus system. Such multi-layered motherboards are expensive and require a large outlay for production. In addition, signal distortions and reflections occur at the bus lines when signals are transferred over a bus system. A space-saving configuration of the individual mutually communicating modules on the motherboard is repeatedly limited by the need for line connections between the individual modules.
A prior art technique for transferring signals between two electronic units which are electrically isolated is to utilize opto-couplers, fiber-optic waveguides, a pulse transformer, a current coupler, or a capacitive coupler.
In an optical coupler, the transmitter and receiver are integrated in a module; the electrical separation between the transmitter and receiver is accomplished by electrically insulating and optically conductive insulation materials. Line connections are usually utilized for the signal transfer from the electronic units to the opto-coupler and from the opto-coupler to the electronic units. The disadvantages of utilizing an opto-coupler are its limited transmission capacity, the limited voltage stability, and the presence of coupling capacities between its input and output. Furthermore, the LED that is utilized as a transmitter in an opto-coupler undergoes an aging process which impairs its normal functioning over time.
When a fiber-optic waveguide is utilized to transfer data, a transmitting unit and a receiving unit are disposed at a distance from one another and connected to each other by the optically conductive waveguide, for instance an optical fiber. It is relatively expensive to use fiber-optic waveguides for data transmission. Furthermore, in this case also, a diode that is utilized on the transmission side undergoes an aging process, which impairs the normal functioning over time. Another known technique for transferring signals between two electrically isolated electronic units is to utilize an impulse transformer comprising two mutually electrically isolated coils on a strongly magnetically conductive core or two coils which are coupled only by air. The disadvantages of utilizing an impulse transformer are that its transmission rate is limited, and that in certain circumstances it has a very large volume and is very heavy. Furthermore, an impulse transformer does not allow transmission of a d.c. voltage signal.
A typical example of a system with two electrically isolated electronic units is a switched-mode power supply wherein the primary side and the secondary side are electrically separated from one another, but an item of information concerning the output voltage at the secondary side must be transferred to the primary side. Other examples include circuit modules comprising a high-voltage switch and an operating and/or control circuit, said operating and/or control circuit being electrically separated from the high-voltage switch in order to prevent a high voltage at the operating and/or control circuit. In what are known as high-voltage cascades, as well, mutually communicating elements must be electrically separated from one another.
Another example of a system wherein a decoupling between a transmitting unit and a receiving unit is required is a half-bridge circuit with a series circuit containing a high-side switch, which is realized as a semiconductor switching element, and a low-side switch, realized as a semiconductor switching element. If the two semiconductor switching elements have the same conductivity type, i.e. they are both constructed as n-conductive transistors such as n-channel MOSFETs, n-channel IGBTs, or npn-bipolar transistors, the problem arises that the actuating of the high-side switch requires a drive signal which is related to a potential at the node shared by the two switches, whereby this potential fluctuates approximately between a reference potential of the circuit and a supply potential of the circuit, depending on the state of the low-side switch. Output signals of a signal processing circuit according to which the high-side switch and the low-side switch are to conduct are usually related to the reference potential of the circuit, typically ground, so that the output signals of the signal processing circuit cannot be utilized directly to actuate the high-side switch. A known technique for adapting the level of the these output signals to the required level for actuating the high-side switch is to transfer the low-side signals of the signal processing circuit by means of the above mentioned opto-coupler or impulse transformer.
Beyond this, in the half-bridge the drive signal can be transferred to the high-side switch by means of current coupling or capacitive coupling. In current coupling, the drive signal is transferred as a pulsed current signal, whereby the pulsed signal can be processed directly or converted into a voltage signal first. In capacitive coupling, the signal is transferred from the processing circuit via a decoupling capacitor, which is able to block the maximum voltage that occurs between the low-side processing circuit and the high-side switch.
According to a technique for distributing a clock signal on a chip while avoiding a line connection as described in On-Chip Wireless Interconnection With Integrated Antennas (Kihong Kim, Hyun Yoon, Kenneth K. O., IEEE Document 0-7803-6441-4/00), a transmitter for sending microwave signals and a plurality of receivers for receiving the microwave signals are provided on a chip.